Hybrid vehicles potentially offer fuel efficiency and vehicle driving range improvements over non-hybrid vehicles. Some hybrid vehicles include an engine and an electrical machine for providing torque to a driveline. The electrical machine may assist engine starting via controlling engine speed during the starting process. However, engine speed during starting may vary from start to start as conditions of the vehicle's electrical system vary. For example, engine cranking torque and speed may vary with battery voltage. Consequently, an amount of air inducted into engine cylinders during starting may vary leading to inconsistent starting time and degraded emissions during some conditions. One example of a hybrid vehicle includes an engine that may be selectively coupled to an electrical machine and a transmission according to vehicle operating conditions.
The inventors herein have recognized the above-mentioned disadvantages and have developed a method of adjusting cylinder air charge of an engine, comprising: adjusting a fuel injection timing of a cylinder to a stroke of the cylinder that varies as a difference between a desired engine speed and an actual engine speed varies and adjusting an amount of fuel supplied to the cylinder in response to cylinder air charge.
By positioning a throttle for an engine start and adjusting a fuel injection timing of a cylinder to a stroke of the cylinder that varies as a difference between a desired engine speed and an actual engine speed varies, it may be possible to reduce engine emissions and provide more consistent starting. In particular, the difference in a desired engine speed and an actual engine speed may be a basis for selecting a stroke during which fuel is injected.
The present description may provide several advantages. Specifically, the approach may reduce engine emissions. Further, the approach may improve engine starting by providing more consistent engine run-ups. Further still, the approach may reduce engine speed variation from engine start to engine start.
The above advantages and other advantages, and features of the present description will be readily apparent from the following Detailed Description when taken alone or in connection with the accompanying drawings.
It should be understood that the summary above is provided to introduce in simplified form a selection of concepts that are further described in the detailed description. It is not meant to identify key or essential features of the claimed subject matter, the scope of which is defined uniquely by the claims that follow the detailed description. Furthermore, the claimed subject matter is not limited to implementations that solve any disadvantages noted above or in any part of this disclosure.